Already happened in 1989 to a degree in Canada, a geomagnetic storm caused a power grid failure, stands to reason that a bigger storm could cause more disruption now we are more reliant on technology.
I can remember talking about this in PCA's "Lounge" years ago while having a discussion on meteorites causing problems to satellites ( the odd one may get struck and knocked out due to plasma strikes).
It is likely to be every bit as serious as the Millennium Bug. Ie a Storm in a teacup- perhaps may be. If any one is really concerned wrap your computer[s] in several layers of Ali- foil and burt 1 metre deep in the Garden[Well maybe the drives any way] '@}
All you have to do is remove a door and use it as a shield. This is the advice given out in the 1960's to protect you from a 50 megaton device exploded at 2000 feet above your head. Not sure if B&Q doors are made to this standard .